With remarkable growths of information communication technology and semiconductor technology, a great variety of electronic devices are increasingly popularized in these days. Additionally, such electronic devices today outgrow their respective traditional fields and hence reach a mobile convergence stage in which the fields of other type devices are incorporated. For example, a smart phone, which has been dramatically popularized in recent years, has ability to offer numerous functions, such as a broadcasting receiver, a multimedia player, an internet access, an electronic organizer, or a social network service (SNS), as well as typical communication functions such as a voice call or a short message service (SMS).
Particularly, recent electronic devices provide a camera function to create and store an image or a video. Further, in order to meet increasing consumers' demands for a high-quality still image and/or video, a higher-resolution camera module is equipped in recent electronic devices.
Recent camera modules provide an autofocus (AF) function to automatically set focus so as to offer a high-quality image or video. For this AF function, an image sensor embedded in the camera module may use various AF techniques such as a contrast-detection AF based on the extraction of contour information from an image, a phase-detection AF based on the use of a phase-difference sensor, a focal-plane phase-detection AF for focusing over a wide area, and the like.